Concept preview

What you will be able to do

1. 01Define pH and pOH with a statement and an equation
2. 02Convert between pH, pOH, [H₃O⁺] and [OH⁻] to the correct significant figures
3. 03Find the pH when strong acids and bases are mixed

The hydronium and hydroxide concentrations in acids and bases span an enormous range, and they are usually very small numbers. In $1.0\ \text{M}$ NaOH the hydroxide concentration is about 100 trillion times the hydronium concentration, and during a neutralization each ion can change by ten million times to equal the other. A plain arithmetic scale of numbers like $[\mathrm{H_3O^+}] = 0.000\,000\,01$ is cumbersome and awkward to read.